Automated antenna trim for transmitting and receiving semiconductor devices

ABSTRACT

A radio frequency communication device and method for tuning an antenna attached thereto are disclosed. A radio frequency communication device is disclosed comprising internal circuitry and an antenna having a plurality of antenna segments associated therewith. Each antenna segment is associated with the antenna in either series or parallel relation through at least one of a fuse and an antifuse. In testing and tuning, a comparison is made to indicate whether the antenna is too short or too long. If the antenna is too short, an antenna segment may be attached to the antenna by initiating an antifuse. If the antenna is too long, an antenna segment may be detached from the antenna by blowing a fuse. If it is indeterminate whether the antenna is too short or too long, an antenna segment may be either attached or detached, the test repeated, and the results of the repeated test compared with the prior test to determine whether the correct action was taken.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/558,581,filed Apr. 26, 2000, now U.S. Pat. No. 6,806,812.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method and apparatus fortuning a transmitting and receiving antenna to a resonant frequency.More particularly, the invention discloses an antenna, such as that usedin conjunction with a radio frequency identification (RFID) tag, havinga plurality of fuses or antifuses, or both, in conjunction therewith.The fuses and antifuses may be initiated to extend or shorten theantenna to tune to a resonant frequency.

2. State of the Art

Radio frequency identification (RFID) technology uses electromagneticenergy as a medium through which to send information. Small radiofrequency communication systems, such as a RFID tag, may be affixed tovarious articles so that the articles may be easily tracked duringmovement from one point to another, or identified, such as through asales transaction. Therefore, one may tag objects such as items,animals, and people, to be identified or tracked automatically via areader. The reader may be connected to a host computer which mayadditionally contain data related to an object's identification codeassociated with the RFID tag. Furthermore, an RFID tag conventionallyalso contains programmed information about an object to which it isattached. Through the use of such information, RFID technology may beused to identify objects automatically and without manual handlingoperations as is required in most bar code systems. In a conventionalRFID tag system, a receiver, a transmitter, an antenna, and memory areimplemented. RFID tags, their use and operation are well known in theart.

Additionally, the general structures and methods of fabricating RFIDtags are well known in the art. RFID tags are enabled to receive, store,and transmit article-identifying data with a remote base station. RFIDtags have been implemented using a variety of methodologies to allow auser to perform any number of desired identification functions. Forexample, RFID tags may comprise read-only or read-write capacity.Additionally, passive RFID tags may be implemented with an internalpower source, or without an internal power source, drawing their powerfrom the radio frequency (RF) energy transmitted from the reader. Aswell, RFID tags may be configured to operate at low, medium or highfrequencies, depending on the needs for a desired application. U.S. Pat.No. 5,777,581 to Lilly et al. (Jul. 7, 1998) even describes an RFsemiconductor circuit which may selectively operate at low, medium andhigh frequencies by switching between three separate antenna systems.

To function with a given system, an antenna must be tuned to theinternal circuitry and signals transmitted and received by the system.Tuning systems and circuitry for adjusting the internal antenna circuitsof RFID tags and similar circuitry are also known in the art. Asindicated in FIG. 1, conventional RFID antenna tuning systems compriseinternal circuitry 2, such as that ordinarily found in an RFID tag, anantenna tuning circuit 4 coupled to the internal circuitry 2, and anantenna 6 coupled to the antenna tuning circuit 4. The antenna tuningcircuit 4 conventionally compares a signal characteristic, such assignal frequency or amplitude, of a received signal with a similar orother characteristic of a signal within the internal circuitry 2. Bymaking adjustments to the antenna tuning circuit 4 settings, the RFIDcircuit may be tuned to a resonant frequency to optimally receivesignals from a remote system transmitting to the internal circuitry 2,and optimally transmit the internal circuitry's 2 response. In this way,the received and transmitted signal amplitudes are maximized and, thus,more reliably interpreted by corresponding circuitry.

Adjustments to the antenna tuning circuit 4 may be made by the internalcircuitry 2, or by a testing device during a testing process. In makingadjustments to the RFID circuit settings to tune to a resonant frequencyof a communication system, conventional antenna tuning circuits modifythe impedance of the antenna tuning circuit 4 by adjusting a variablecapacitive or variable inductive element, or both. Once a modificationis made, or coincidental with the adjustment being made, the signalcharacteristics are again compared and more adjustments made until theresonant frequency settings have been determined. Examples ofconventional radio frequency antenna communication systems using variousforms of impedance adjustments are shown and described in U.S. Pat. Nos.5,970,398 to Tuttle (Oct. 19, 1999), 5,777,581 to Lilly et al. (Jul. 7,1998), 5,491,715 to Flaxl (Feb. 13, 1996), 5,448,110 to Tuttle et al.(Sep. 5, 1995), 4,780,724 to Sharma et al. (Oct. 25, 1988), and4,486,723 to Lysobey (Dec. 4, 1984), the disclosures of which are herebyincorporated herein by reference.

The internal antenna tuning circuit components, however, undesirably addto the size of the device, particularly in RFID applications where adesire is for a smaller system. Additionally, by interposing capacitiveand inductive components between the antenna and the internal circuitry,additional power is consumed in activating those elements, andadditional heat is produced. Furthermore, radio frequency communicationdevices operating at higher frequencies (several hundred megahertz) aredifficult to tune using variable circuit impedance elements such asinductors and capacitors. It is therefore desirable to have a smallradio frequency transponder circuit, such as that used in RFID tags,which does not require an additional internal antenna tuning circuit sothe overall system can consume less power, produce less heat and useless space.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for tuning a radiofrequency antenna, such as that used in radio frequency identification(RFID) tags, to a semiconductor circuit using additional antennasegments coupled to the antenna by fuses and antifuses. According to afirst embodiment of the invention, at least one antenna for a RFID tagis disclosed. The antenna comprises a main antenna portion, a pluralityof antenna portions, each coupled to the main antenna portion by a fuse,and a plurality of antenna portions, each separated from the mainantenna portion by an antifuse. A method of the present invention uses atesting device having probe hardware, software and antenna tuninghardware to test one of the responses of the antenna to a test signaland a signal transmitted from the RFID tag. Based upon the response ofthe antenna, the testing device may initiate a connect or disconnectoperation to attach an additional antenna segment through an antifuse ifthe antenna is determined to be too short, or detach an antenna segmentthrough a fuse if the antenna is determined to be too long.Alternatively, the testing device may do nothing if the antenna respondswithin specifications. Additionally, if the testing device determinesthat the antenna response is not within specifications but cannotdetermine whether the antenna is too long or too short, a method of thepresent invention has the testing device initiating either a fuse blowoperation or an antifuse connect operation and then retests the antennasystem to evaluate whether the antenna response improved or became worseas a result of the change. Further testing is based upon the response ofthe modified antenna. If all of the fuses have been blown, or all of theantifuses have been connected and the antenna still does not operatewithin specifications, the RFID tag is rejected. The antenna segmentsattached to the main antenna through fuses and antifuses may be attachedin series or in parallel, though series connection is most preferred.

A second embodiment of the invention discloses an RFID tag havinginternal circuitry, a main antenna and a plurality of antenna segments,each coupled in series to the main antenna through a fuse. The antennasystem may be intentionally fabricated such that at least one fusedsegment needs to be detached for the antenna to operate withinspecifications. A method of the present invention of testing the RFIDtag includes testing the antenna using a testing device such that anantenna response is measured and a fuse is blown if the antenna isdetermined to be too long or out of specification limits.

A third embodiment of the invention discloses an RFID tag havinginternal circuitry, a main antenna and a plurality of antenna segments,each attachable to the main antenna in series through an antifuse. Theantenna system may be intentionally fabricated such that at least oneantifused segment needs to be attached for the antenna to operate withinspecifications. A method of the present invention of testing the RFIDtag includes testing the antenna using a testing device such that anantenna response is measured and an antifuse is connected if the antennais determined to be too short or out of specification limits.

A radio frequency communication system is disclosed comprising aprocessor, a memory device, an input, an output and a storage device, atransceiver and a plurality of RFID tags, each having internalcircuitry, a main antenna and a plurality of antenna segments, eachassociated with the main antenna by at least one of a fuse and anantifuse.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The nature of the present invention as well as other embodiments of thepresent invention may be more clearly understood by reference to thefollowing detailed description of the invention, to the appended claims,and to several drawings herein, wherein:

FIG. 1 is a block diagram of a prior art radio frequency identification(RFID) circuit;

FIG. 2 is a block diagram of a RFID circuit according to a firstembodiment of the present invention and a testing device;

FIG. 3 is a block diagram of a RFID circuit depicting antenna segmentscoupled to a main antenna in parallel;

FIG. 4 is a block diagram of a RFID circuit depicting two main antennas,each having antenna segments coupled thereto;

FIG. 5 is a block diagram of a RFID circuit according to a secondembodiment of the present invention;

FIG. 6 is a block diagram of a RFID circuit according to a thirdembodiment of the present invention; and

FIG. 7 is a block diagram of a radio frequency communication system.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 2 is a block diagram of a radio frequency identification(RFID) tag circuit 8 coupled to a testing device 10 according to a firstembodiment of the present invention. The RFID tag circuit 8 comprisesinternal circuitry 12, a main antenna 14, a plurality of antennasegments 16 coupled to the main antenna 14 in series through fuses 18,and a plurality of antenna segments 20 coupleable to the main antenna inseries through antifuses 22. The internal circuitry 12 of the RFID tagcircuit 8 may be one of many well known RFID tag or patch circuits knownin the art such as that disclosed in U.S. Pat. No. 5,448,110 to Tuttleet al. (Sep. 5, 1995) (including a wake-up circuit, receiver,transmitter, control logic, memory and one or more batteries), or thatdisclosed in U.S. Pat. No. 5,497,140 to Tuttle (May 5, 1996) (includinga sleep/wake-up circuit, receiver, transmitter, control logic, memoryand no batteries). One of ordinary skill in the art will readilyunderstand how to adapt the principles of the present invention to anyradio frequency communication device known in the art.

Also shown in FIG. 2 is a testing device 10 comprising test probehardware 24, software 26, and antenna tuning hardware 28. The test probehardware 24 includes a probe 30 for coupling to the RFID tag circuit 8.Conventionally, a RFID tag circuit is tested prior to its initial use,and preferably after final packaging, to ensure that the antenna 14 ofthe circuit 8 is in tune with the internal circuitry. To do this, atesting device 10 measures the antenna 14 response to various incomingand outgoing signals with respect to the internal circuitry.Conventionally, if it is determined that the antenna would respond moreoptimally with more or less impedance, a value of a variable inductor orcapacitor is respectively increased or decreased to optimize the antennatuning, or match the impedance of the antenna to the system. Suchtesting and tuning circuit adjustment devices and methods are well knownto one of ordinary skill in the art.

According to this first embodiment of the present invention, rather thanusing variable capacitors or inductors to adjust the antenna response tosignals, antenna segments 16 and 20 are associated with the main antenna14 through antifuses 22 or fuses 18. Because the testing sequence isprimarily controlled through test software 26, a software programmer ofordinary skill in the art may readily modify the software 26 to blow afuse 18 or initiate an antifuse 22, rather than increase or decrease theinductance or capacitance of an antenna impedance matching circuit, inresponse to an antenna test. By removing a portion of an antenna coupledto the main antenna through detaching an antenna segment 16 by blowing afuse 18, the impedance of the antenna is decreased. By adding a portionof an antenna to the main antenna through attaching an antenna segment20 by initiating an antifuse 22, the impedance of the antenna isincreased.

The fuses used for the antenna may be any of those commonly known in theart including, but not limited to, electrically-blown or laser-blownfuses, and may be fabricated on a semiconductor substrate, such as aVLSI fuse, or on a film, such as a RFID package overlay. It is believedthat one of ordinary skill in the art will understand how to fabricateantenna segments 16 coupled to a main antenna 14 through fuses 18.Antifuses 22, their use and fabrication are similarly well known in theart.

It should be noted that drastic adjustments in the overall antennalayout and arrangement caused by adding or removing antenna segments 16and 20 may affect the distribution and reception pattern of the antenna14. It is preferred that the antenna segments 16 and 20 be relativelyshort with respect to the overall length of the antenna 14, and that thesegments 16 and 20 follow the general layout of the main antenna 14.Each antenna layout and desired application is different, however, andone of ordinary skill in the art will readily be able to incorporateadditions or subtractions of antenna segments 16 and 20 into an existingantenna scheme.

As shown in FIG. 3, rather than associating the antenna segments 16 and20 with the main antenna 14 in series through fuses 18 and antifuses 22as shown in FIG. 4, antenna segments 24 and 26 may be associated with amain antenna 28 in parallel, though series association is mostpreferred. As shown in FIG. 4, an RFID tag 30 may have more than onemain antenna 32 and 34 coupled to the internal circuitry 36. It iscontemplated, however, that each main antenna 32 and 34 may havesegments 38 and 44 associated therewith through fuses 40 or antifuses42, or both.

Shown in FIG. 5 is a block diagram of a RFID circuit 46 according to asecond embodiment of the present invention. According to this secondembodiment, RFID circuit 46 includes a plurality of antenna segments 50coupled in series to a main antenna 48. The combination of the mainantenna 48 and fused antenna segments 50 may be intentionally designedand fabricated to be longer than needed to tune to the internalcircuitry 54 so that at least one fuse 52 will need to be blown during atesting operation. In this way, antifuses which lengthen the mainantenna 48 by coupling antenna segments to the main antenna 48 will notbe needed. In a testing operation, the RFID circuit 46 is tested and theantenna response monitored. If the antenna response, as interpreted by atesting device, indicates that the antenna 48 is too long, a fuse 52farthest from the main antenna 48 in the series is blown and the testingoperation repeated with a second, third, etc. fuse being blown as neededuntil the antenna response is within antenna specifications. If theantenna response, as interpreted by the testing device, indicates thatthe antenna 48 is too short, or after all the fuses 52 are blown, theantenna 48 is still too long, the RFID circuit 46 is rejected for use inits present application.

Shown in FIG. 6 is a block diagram of a RFID circuit according to athird embodiment of the present invention. According to this thirdembodiment, a RFID circuit 55 includes a plurality of antenna segments56 associated in series with a main antenna 58. The main antenna 58 maybe intentionally designed to be shorter than needed to tune the internalcircuitry 62 so that at least one antifuse 60 will need to be initiatedduring a testing sequence. In this way, fuses which shorten the mainantenna 58 by decoupling antenna segments from the main antenna 58 willnot be needed. In a testing operation, the RFID circuit 55 is tested andthe antenna response monitored. If the antenna response, as interpretedby a testing device, indicates that the antenna 58 is too short, a firstantifuse 60 closest to the main antenna 58 is initiated and the testingoperation repeated with a second, third, etc. antifuse being initiatedas needed until the antenna response is within antenna specifications.If the antenna response, as interpreted by the testing device, indicatesthat the antenna 58 is too long, or after all the antifuses 60 have beeninitiated, the antenna 58 is still too short, the RFID circuit 55 isrejected for use in its present application.

Shown in FIG. 7 is a block diagram of a radio frequency communicationsystem 100 including RFID tags 116, 118 and 120, each having an antenna122, 124 and 126 comprising a main antenna and antenna segmentsassociated with the main antenna according to one or more embodiments ofthe present invention. The radio frequency communication system 100includes a processor 104 for performing various computing functions,such as executing specific software to perform specific calculations ortasks and coordinate identification information. Additionally, the radiofrequency communication system 100 includes one or more transmitters 105and receivers 106 to send and receive information from the RFID tags116, 118 and 120 to the processor 104. The radio frequency communicationsystem 100 also includes one or more input devices 108, such as akeyboard or a mouse, coupled to the processor 104 to allow an operatorto interface with the radio frequency communication system 100. Theradio frequency communication system 100 also includes one or moreoutput devices 110 coupled to the processor 104, such output devicesincluding such outputs as a printer, a video terminal or a networkconnection. One or more data storage devices 112 are also conventionallycoupled to the processor 104 to store or retrieve data from externalstorage media. Examples of conventional storage devices 112 include hardand floppy disks, tape cassettes, and compact disks. The processor 104is also conventionally coupled to a cache memory 114, which is usuallystatic random access memory (“SRAM”), and to DRAM 102.

Though depicted as dipole or linear antennas in the various embodimentsherein, it will be understood by one of ordinary skill in the art thatthe principles of this invention may be readily applied to any antennaor antenna array configuration, such as a loop, coil or a bowtieantenna. Furthermore, though a particular number of antenna segments mayhave been shown as illustrative of the present invention, it will beunderstood by one of ordinary skill in the art that any number ofantenna segments, and antenna segments of varying sizes, may beassociated with a main antenna through fuses and antifuses. One ofordinary skill in the art may readily adapt the principles of thepresent invention to a particular RFID architecture, layout andapplication. Additionally, as will be clear to one of ordinary skill inthe art, because antennas in the art are formed in embodiments on asemiconductor substrate, and in embodiments off the semiconductorsubstrate but in electrical contact with the substrate, and fuses andantifuses may be formed either on or off of a semiconductor substrate,the present invention may readily be formed on or off of a semiconductorsubstrate.

By adjusting the tuning of an RFID circuit antenna through adjusting thelength of the antenna rather than adjusting the values of capacitive andinductive components attached to the antenna, less power is consumed,less heat is produced and devices operating at higher frequencies aremore easily tuned.

Although the present invention has been shown and described withreference to a particular preferred embodiment, various additions,deletions and modifications that are obvious to a person skilled in theart to which the invention pertains, even if not shown or specificallydescribed herein, are deemed to lie within the scope of the invention asencompassed by the following claims.

1. A radio frequency communication device comprising: internalcircuitry; at least one antenna coupled to the internal circuitry forevaluating an antenna response to at least one test signal for the atleast one antenna to do one of accepting the radio frequencycommunication device, rejecting the radio frequency communicationdevice, coupling an antenna segment to the antenna, and detaching anantenna segment from the antenna; and at least one antenna segmentcoupled to the at least one antenna by one of a fuse which may be blownor an antifuse.
 2. The radio frequency communication device of claim 1,further comprising a plurality of antenna segments coupled by fuses inseries with the at least one antenna segment.
 3. The radio frequencycommunication device of claim 1, wherein the at least one antennasegment comprises a plurality of antenna segments, each coupled to theat least one antenna in parallel by a fuse.
 4. The radio frequencycommunication device of claim 1, wherein the at least one antennacomprises at least two antennas, each coupled to at least one antennasegment by a fuse.
 5. The radio frequency communication device of claim1, wherein the radio frequency communication device is a radio frequencyidentification tag.
 6. The radio frequency communication device of claim1, wherein the internal circuitry comprises at least one of a sleepcircuit, a wake-up circuit, a receiver, a transmitter, control logic,memory and at least one battery.
 7. The radio frequency communicationdevice of claim 1, further comprising at least one other antenna segmentassociated with the at least one antenna through an antifuse.
 8. Theradio frequency communication device of claim 7, further comprising aplurality of other antenna segments associated in series with the atleast one antenna segment and connected through a plurality ofantifuses.
 9. The radio frequency communication device of claim 7,wherein the at least one other antenna segment comprises a plurality ofantenna segments, each associated with the at least one antenna inparallel through an antifuse.
 10. A radio frequency communication devicecomprising: internal circuitry; at least one antenna coupled to theinternal circuitry for evaluating an antenna response to at least onetest signal for the at least one antenna to do one of accepting theradio frequency communication device, rejecting the radio frequencycommunication device, coupling an antenna segment to the antenna, anddetaching an antenna segment from the antenna; and at least one antennasegment associated with the at least one antenna through one of a fusewhich may be blown and an antifuse.
 11. The radio frequencycommunication device of claim 10, further comprising a plurality ofantenna segments associated in series with the at least one antennasegment through a plurality of antifuses.
 12. The radio frequencycommunication device of claim 10, wherein the at least one antennasegment comprises a plurality of antenna segments, each associated withthe at least one antenna in parallel through an antifuse.
 13. The radiofrequency communication device of claim 10, wherein the at least oneantenna comprises at least two antennas, each associated with at leastone antenna segment through an antifuse.
 14. The radio frequencycommunication device of claim 10, wherein the radio frequencycommunication device is a radio frequency identification tag.
 15. Theradio frequency communication device of claim 10, wherein the internalcircuitry comprises at least one of a sleep circuit, a wake-up circuit,a receiver, a transmitter, control logic, memory and at least onebattery.
 16. A radio frequency communication system comprising at leastone of a transmitter, a receiver, a processor, an input device, anoutput device, data storage, and memory, the system further comprisingat least one radio frequency identification tag associated therewith,the radio frequency identification tag comprising internal circuitrycoupled to an antenna for evaluating an antenna response to at least onetest signal for the at least one antenna to do one of accepting theradio frequency identification tag , rejecting the radio frequencyidentification tag, coupling an antenna segment to the antenna, anddetaching an antenna segment from the antenna, the antenna including atleast one antenna segment associated therewith through at least one of afuse and an antifuse.
 17. The radio frequency communication system ofclaim 16, wherein the antenna includes at least one antenna segmentassociated therewith through each of the fuse and the antifuse.
 18. Theradio frequency communication system of claim 16, wherein the at leastone antenna segment is associated with the antenna in series.
 19. Theradio frequency communication system of claim 16, wherein the at leastone antenna segment is associated with the antenna in parallel.
 20. Theradio frequency communication system of claim 16, wherein the at leastone antenna segment comprises a plurality of antenna segments coupled inseries by a plurality of fuses.
 21. The radio frequency communicationsystem of claim 16, wherein the at least one antenna segment comprises aplurality of antenna segments associated in series through a pluralityof antifuses.
 22. A method of forming an antenna for a radio frequencycommunication device, the method comprising: forming an antenna and aplurality of antenna segments on a substrate; associating the pluralityof antenna segments in series or in parallel with the antenna by formingat least one of a fuse and an antifuse therebetween; evaluating anantenna response to at least one test signal; and in response to anevaluation result, doing one of: accepting the radio frequencycommunication device; rejecting the radio frequency communicationdevice; coupling an antenna segment to the antenna; and detaching anantenna segment from the antenna.
 23. The method of claim 22, whereinforming the antenna and the antenna segments on the substrate comprisesforming the antenna and the antenna segments on a semiconductorsubstrate.